The class of work machines utilized for agricultural, industrial and other uses termed as work machines typically operates in a highly contaminated environment, thus making the function of cleaning air used by an air breathing internal combustion engine especially important. Nowhere is this as important as in the agricultural field where the work machine is in a field harvesting crops which generates significant contaminants in the form of debris and particles. It is necessary for such machines to have a pre-cleaner since the ambient level of particles is so significant. An air filter alone would quickly become clogged. In the present environment, pre-cleaners are employed upstream of the primary filter for the air intake system of the engine. Such pre-cleaners may take various forms but, as used commercially, usually are systems imparting a centrifugal motion to the air leading to the primary air filter inlet. Such centrifugal motion causes the denser particles to be thrown to the outer periphery of the pre-cleaner, leaving the less contaminated air to exit to the primary filter through a central inlet. Such air pre-cleaners have an outlet for the accumulated particles and some units have that outlet connected to an aspirator positioned in a muffler in the engine exhaust system. Problems can occur with an arrangement of this type since the connection to the exhaust system has the potential of increasing back pressure and thereby decreasing the efficiency of the engine. In addition, the performance of the flow through the engine exhaust system depends significantly on engine load thereby generating a variable removal of particles from the pre-cleaner.
Other approaches seek to remove excess particles from a pre-cleaner by utilizing the pressure drop created by the engine cooling fan since this fan is solely dependent on engine rpm and not engine load. However this too has limitations on its effectiveness.
What is needed in the art therefore is a system in which excess particles from an engine pre-cleaner are removed consistently and with a minimum of parasitic losses.